Today, the CMP is becoming an indispensable technique for planarization of an interlayer dielectric film, formation of a plug inside a via hole, formation of an embedded metal wiring, and so forth (refer to Japanese Unexamined Patent Publication JP-A 2004-193495, for example).
Formation of an embedded metal wiring involving a CMP process will be described with reference to FIG. 14.
As shown in FIG. 14A, a concave groove for forming a wiring is formed in a dielectric film 10 such as an oxide film formed on a semiconductor substrate, and a barrier metal film 11 made of titanium nitride (TiN), etc. is then deposited over an entire surface of the dielectric film 10, thereafter depositing on the barrier metal film 11 a metal film 12 for forming a wiring made of tungsten (W), etc. over the entire surface so as to fill the groove.
Next, as shown in FIG. 14B, the CMP is applied to the metal film 12 for forming a wiring so that the metal film 12 for forming a wiring in an unnecessary region and the barrier metal film 11 lying thereunder are polished to be thereby removed, thus leaving the metal film 12 for forming a wiring only inside the groove. The metal wiring is thus formed.
In adopting such CMP to form the metal wiring however, the polishing is conducted using, as a polishing slurry, a slurry which is high in a polishing speed (polishing rate) for the metal film for forming a wiring, for example, a slurry containing fumed silica as abrasive grains for polishing, in order to shorten a length of polishing time to enhance the throughput, thus causing so-called dishing that a central part of the wide embedded wiring 12 is polished in a region where the groove is wide, and so-called erosion that the narrow embedded wiring 12 and the dielectric film 10 therearound are simultaneously polished in a region where the grooves densely exist, as shown in FIG. 15.
An uneven surface formed by such dishing and erosion easily causes a difference in level of a dielectric film in an upper layer of a multilayered wiring, thus posing a problem such as electrical short circuit due to a metal film for forming a wiring which remains after the polishing, when the wiring film on the upper layer is formed.